I agree if that's all you're worried about tracking are those basic stats. If you want all your abilities, spells, attacks, etc. managed in HLO or the campaign theater module then there's a way to accomplish that too. The only disadvantage to the Stand in is that it's for PCs only, so scripts won't work as well with that approach. In order to use the scripts and the resolve scene features you can create a basic NPC stand-in using what I described above if you don't want to spend the time creating the NPC with everything.

stand-ins are technically supposed to be for PCs only (for now), but if you create a "PC" stand-in on the Cast Members screen rather than the PCs and Players screen, you can use it in scripts just like any other NPC or monster cast member.

but you're right, stand-ins have some major limitations when it comes to special abilities. currently you can assign them Feats, but not spells or class abilities. for now i track any special abilities (like the Caustic Wolf's acid immunity and Howl) by writing them out in the Notes section of the stand-in, but i agree it's not ideal.

Good to know about the stand-in for cast members. Thanks for that tip!

OK, so I need to know if I am doing something dumb or there's just something missing here. This is my first time trying the campaign stuff, decided to give it a go with a patron and a few Apprentice accounts.

I am setting up for Age of Ashes, creating scripts for easy encounter deployment. I dig in and look around, it looks straightforward enough - add a fire mephit, etc.

Then I get to the first encounter with an actual NPC.

Cool, I will import him in from the Age of Ashes module I bought. He's not there. Ugh.
Fair enough, he's a level 2 human fighter. I go "Add NPC/Monster", and Human is not in the race list. Ugh again.
So, I try a stand-in PC, and there's no way to add gear so the attacks work but I can't roll damage. Ugh a third time.

So I guess I am expected to reverse engineer a basic stat block all the way into a real PC for every class-based NPC in the campaign, from blocks that for high level NPCs can take hours to do? There's really no other way?

Instead of reverse engineering look at the screen shots I provided in an earlier post on this forum. You can use a custom ancestry and set things like hp and speed with that. Then use the overrides to set the other stats and abilities. I've recently discovered that you can use the custom boons to create custom abilities if they aren't available through the overrides. It's much easier than trying to reverse engineer everything.

Ah, I read that, but it didn't click. I will give it a shot, thanks for the response!

A key part of the problem here is that the official PF2 rules for NPC creation are only releasing today from Paizo (as part of the Gamemastery Guide). We'll have that book available (and the NPC/monster rules) next Wednesday.

Along with the GMG release next week, we'll also be including some new capabilities that are not tied to the purchase of any add-ons. This should allow you to readily enter the assorted NPCs and monsters from Age of Ashes.

We had wanted to get all that stuff released today, but it's a little behind due to the crunch getting everything into place for group licensing.

In the interim, the approach suggested by @Sjmarshall is probably your best bet.

Awesome, great to hear! How about the GM content pack for Age of Ashes? That will include all the NPCs and AP-specific monsters, correct? Can you give a very rough ballpark guesstimate of when that will release?

This is where we got ourselves into trouble in the past, so I'm not gonna give any estimates, as much as I would like to. What I can do, though, is very definitely confirm that adding the GM content is on the roadmap. And there's another very cool feature that dovetails closely with GM content, but I'm not yet sure which of the two will be implemented first.

That's great news!

As an aside to my earlier post, it's pretty obvious that the NPCs in this first adventure were made using pre-release rules. There's no way to "legally" generate them as PCs without fudging things via custom modifiers and adding feats and backgrounds that won't affect their combat oriented abilities (such as adding weapon familiarity to fill out the ancestry trait slot, even though they aren't using any weapons that benefit from it).

In other words, I don't envy the person who has to go through and make these guys for said GM content pack, but I will gladly pay you for one so I don't have to. :)